Surface wettability controllable polyimides bearing long-chain alkyl groups via phenyl ester linkages by ultraviolet light irradiation

Abstract

The novel polyimides and copolyimides are synthesized from the diamines having three long-chain alkyl groups connected by phenyl ester linkages, 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride or diphenylsulfonetetracarboxylic dianhydride as a tetracarboxylic dianhydride, and 4,4’-diaminodiphenylether as a diamine comonomer. These polyimides show good film-forming ability and good thermal properties. The thin films of obtained polyimides were irradiated by ultraviolet (UV) light ( λmax = 254 nm), and the contact angles for the water decreased from near 100° (hydrophobicity) to near 20° (hydrophilicity) in proportion to irradiated UV light energy. From the result of attenuated total reflectance analysis, it is recognized that the hydrophobic long-chain alkyl groups on the polyimide surface decrease and the hydrophilic groups such as carboxyl groups and hydroxyl groups generate on their surface. Thus, the surface wettability of these polyimides can be controlled by UV light irradiation, and this method is expected to be applied in the field of printed electronics.